The firmware update released this morning for the Canon R5 allows the camera to work better with the accelerometer data coming from the new big white lenses the RF400mm F/2.8 L IS USM and the RF600mm f/4 L IS USM. The effect on the stabilization for those lenses is “extremely significant” according to a regular reader of Camnostic who was asked to test this specific element after updating his R5.
The original release of those lenses was more than disappointing for many sports and wildlife shooters, as the optical designs were unchanged from the latest EF versions of the lenses, and there was hope that a lens IS + IBIS effect would be seen, granting the lenses more than 5 stops of stabilization. This appears to have happened finally with the new firmware upgrade.
With the new R3 camera being tested prior to release, there is hope that several new features designed into that camera may leak over to the R5 in this and potentially future firmware updates.